1. Field of the Invention
The present invention relates to an image transfer apparatus in which an image bearing sheet, on which an image is formed by a thermal transfer printer or a laser thermal transfer printer (or any type of a printer such as an ink jet printer etc. which can transfer an image on a sheet to be transferred), and the sheet to be transferred are laminated and the two sheets thus laminated are passed between a pair of heat rollers thereby to transfer the image formed on the image bearing sheet on the sheet to be transferred.
2. Description of the Related Art
When preparing a printing plate from a color manuscript and forming many printed sheets based on the printing plate, proof print is performed to confirm the finished image and then the formal printing is performed. In this case, a color proof is prepared in the proof printing process and the finished image is confirmed. Such a color proof etc. is obtained in a manner that an image is thermally transferred on an image bearing sheet by a thermal printer etc. and the image formed on the image bearing sheet is transferred on a sheet on which the image is to be transferred (hereinafter called an image transfer sheet) by an image transfer apparatus.
FIG. 10 shows a conventional image transfer apparatus. In the figure, a reference numeral 1 depicts an image transfer apparatus. The image transfer apparatus 1 is provided with a pair of heat rollers 41, 42 disposed in an opposed manner along the vertical direction, and nip rollers 51, 52 disposed at the downstream side of the heat rollers in an opposed manner along the vertical direction. A heat cover 4 surrounds the heat rollers 41, 42 to prevent the heat dissipation from the heat rollers 41, 42. A protecting transfer cover 5 surrounds the outer side of the heat cover and the nip rollers 51, 52. An insertion table 2 is provided at the inlet side of the image transfer apparatus 1 and an ejection table 3 is provided at the ejection side thereof.
The heat rollers 41, 42 are formed by aluminum material etc., for example, and the outer peripheral surfaces thereof are covered by covering layers made of rubber etc. A heater is provided at the center portion of each of the heat rollers 41, 42. One (for example, the lower side roller) of the heat rollers 41, 42 disposed in an opposed manner along the vertical direction is a driving roller and the other thereof (the upper side roller) is a driven roller. Laminated two sheets of an image bearing sheet and an image transfer sheet are passed between the upper and lower heat rollers 41, 42 while being heated and pressed, so that an image of the image bearing sheet is transferred on the image transfer sheet. Thereafter, the image bearing sheet is manually peeled from the image transfer sheet, thereby to obtain the sheet on which the image is transferred.
Conventionally, the image transfer apparatus 1 has been employed in the following two manners so as to transfer an image.
1) One of the methods is arranged as shown in FIG. 11 in a manner that an image bearing sheet R is laminated on an image transfer sheet P, then the laminated sheets are passed as they are between the heat rollers 41, 42 while being heated and pressed thereby to transfer an image of the image bearing sheet R on the image transfer sheet P, then the laminated sheets are conveyed by the nip rollers 51, 52 and ejected from the ejection table 3. However, in this case, when the laminated sheets.are passed between the heat rollers, the image bearing sheet and the image transfer sheet are bent to form uneven wrinkles (hereinafter referred to wrinkles) thereon caused by the difference of amounts of expansion or shrinkage, the difference of thermal expansion coefficients, the difference of the coefficients of moisture absorption etc. between the image transfer sheet P and the image bearing sheet R due to the difference of the materials thereof.
2) In order to obviate such a problem, the other method using a carrier for the image transfer apparatus has been employed. FIG. 12 shows the laminating method using the image transfer apparatus carrier.
In the figure, a reference numeral 9 depicts the image transfer apparatus carrier which is configured by a carrier board 91 formed by aluminum etc. with a thickness of 0.3 mm, a cover sheet 92 formed by polyimide etc. with a thickness of 0.2 mm which covers only the vicinity of the tip portion of the carrier board 91 at the moving direction side thereof, and a heat-resistant tape 93 for fixing the cove sheet 92 to the carrier board 91.
The image transfer apparatus carrier 9 is employed in the following manner. First, the cover sheet 92 is opened, then laminated sheets of an image transfer sheet P and an image bearing sheet R are inserted between the cover sheet 92 and the carrier board 91, and the cover sheet 92 is closed thereby to sandwich the laminated two sheets from the major surface of the image bearing sheet and the rear surface of the image transfer sheet by the cover sheet and the carrier board. Then, in this state, the laminated two sheets held by the cover sheet and the carrier board are conveyed in a manner that the heat-resistant tape 93 side thereof is conveyed as the head toward and inserted between the heat rollers 41, 42.
When the image transfer apparatus carrier is employed in this manner, both the image transfer sheet P and the image bearing sheet R are sandwiched between the carrier board 91 and the cover sheet 92 and passed between the heat rollers 41, 42 while being held by the image transfer apparatus carrier 9. Thus, both the sheets can be prevented from causing the wrinkles.
However, although the wrinkles can be prevented from being caused by using the image transfer apparatus carrier 9, since the heat is absorbed by the aluminum board, the heat transmission efficiency to the laminated sheets is degraded, so that it is required to lower the conveying speed of the laminated sheets to about {fraction (1/10)} of that of the conventional method. Otherwise, it is required to set the temperature of the heat rollers at the value higher than.that of the conventional method. Thus, there arises such a problem that the consumption of electricity increases, the heat insulated structure becomes exaggerative, and the heat-resistant temperature of the members to be used is required to be raised, or the like.
The invention has been made in view of the aforesaid problem, and an object of the present invention is to provide an image transfer method and an image transfer apparatus which can transfer an image on a sheet on which an image is to be transferred at a normal sheet conveying speed and with normal consumption amount of electricity without using an image transfer apparatus carrier and without causing wrinkles.
In order to attain the aforesaid object, an image transfer method according to the first aspect of the invention is arranged in a manner that in an image transfer method wherein an image bearing sheet on which an image is formed and a sheet on which an image is to be transferred are laminated, and the two sheets thus laminated are passed between a pair of heat rollers from an insertion table thereby to transfer the image formed on the image bearing sheet on the sheet on which the image is to be transferred, the method comprising the steps of:
placing the image bearing sheet on the insertion table;
laminating the sheet on which an image is to be transferred on the image bearing sheet; and
inserting the two sheets thus laminated between the pair of heat rollers.
According to such an arrangement, since the sheet on which an image is to be transferred likely absorbing moisture is placed on the image bearing sheet, the moisture contained in the sheet on which an image is to be transferred will be evaporated therefrom upward and so both the sheets can be prevented from causing image transfer failure such as wrinkles. Further, such a phenomenon scarcely occurs that vapor stays between the two sheets thus laminated to partially cause the extension or shrinkage of the sheet on which an image is to be transferred thereby to occur the image transfer failure.
According to the second aspect of the invention, said step of inserting is a step of inserting the sheet and the image bearing sheet so that the sheet takes precedence over the image bearing sheet by a constant length.
According to the third aspect of the invention, said constant length is set so as to prevent a failure of the sheet and the image bearing sheet feeding called xe2x80x9cjamxe2x80x9d.
According to the forth aspect of the invention, said insertion table is provided with marks thereon corresponding to a positional relation of the image bearing sheet and the sheet on which an image is to be transferred, said two sheets are inserted according to the marks.
According to the fifth aspect of the invention, 5. An image transfer apparatus method according to claim 1, wherein from the beginning of inserting step, until tip portions of the two sheets thus laminated are nipped by an operator.
According to the sixth aspect of the invention, said insertion table includes notch portions are arranged in a manner that an operator can hold the two sheets thus laminated.
According to the seventh aspect of the invention, the image bearing sheet and the sheet on which an image is to be transferred are laminated in such a positional relation that the sheet on which an image is to be transferred is inserted between the pair of heat rollers prior to the image bearing sheet by a length of 21 mm or more.
According to such an arrangement, the sheet conveying procedure can be scarcely failed and so the image transfer procedure can be performed satisfactorily between the image bearing sheet and the sheet on which an image is to be transferred.
According to the eighth aspect of the invention, an image transfer apparatus is arranged in a manner that an insertion table is provided with marks thereon corresponding to the positional relation of the image bearing sheet and the sheet on which an image is to be transferred.
According to such an arrangement, the satisfactory positional relation between the image bearing sheet and the sheet on which an image is to be transferred described above can be easily obtained by merely placing the image bearing sheet and the sheet on which an image is to be transferred in accordance with the marks.
According to the ninth aspect of the invention, an image transfer apparatus is arranged such that an insertion table includes notch portions which are arranged in a manner that an operator can hold the two sheets thus laminated until tip portions of the two sheets thus laminated are nipped.
According to such an arrangement, since the laminated sheets can be inserted in a level state without lifting them, the sheets scarcely cause the wrinkles. Further, since the laminated sheets are nipped when the rear ends of the laminated sheets reach the end portions of the notch portions of the insertion table, an operator may take the hands off the sheets at this time. Thus, the insertion procedure can be performed easily.
According to the tenth aspect of the invention, a mark indicative of a position of the leading edge of a main sheet on an insertion table is located downstream of a mark indicative of a position of the leading edge of an image receiving sheet as viewed in the transporting direction.
According to the eleventh aspect of the invention, said insertion table includes a cutout having a length long enough to hold an image receiving sheet and a main sheet, both being superimposed one on the other by an operator, till the leading edges of said image receiving sheet and said main sheet are nipped with a first nip roller pair.
With such a construction, the sheets being superimposed one on the other can automatically and horizontally be inserted into the nip roller pair by the belt conveyor. Therefore, there is little chance of creasing the sheets.
According to the twelfth aspect of the invention, said insertion table includes a slide table for transporting an image receiving sheet and a main sheet, both being superimposed one on the other, till the leading edges of said image receiving sheet and said main sheet are nipped by a first nip roller pair.
With such a construction, in a manner that after the image receiving sheet and the main sheet having been positioned to each other and superimposed one on the other are placed on the insertion table, the slide table is merely moved, those sheets being superimposed one on the other may reliably be fed into the nip roller pair. Therefore, those sheets are little creased.